Bituminized felt



Patented June 5, 1934- PATENT OFF-l 1,961,946 BITUMINIZED FELT Milton 0.Schur and Walter L. Hear-n, Berlin,

N. H., assignors to Brown Company, Berlin, N. E, a corporation of MaineNo Drawing.

Application January 12, 1933,

Serial No. 651,358

2 Claims.

- pose of covering the walls, roofs, and other parts of a building and,when properly finished, as with linseed-oil-paint ornamentation, areserviceable as floor coverings or the like. The presgoing purposes werefabricated from cheap rags as the main raw material. The rags wereplaced in the usual hollander or beater engine, wherein they were beatenin the presence of water until the roof, undergo flexing.

a smooth pulp or halfstufi, the fibers of'which were of sufficientlyreduced length to be feltable,

was obtained, whereupon the pulp was appropriately diluted with waterand delivered to the tear resistance to withstand rough handling.

during the laying of shingles cut therefrom, particularly when theshingles are interlocked bytabs 01' similar elements. Moreover, suchshingles may be insufiicientlyflexible to withstand cracking when theirinterlocking portions are subjected to comparatively sharp bendingduring assembly on a roof. The fact is that the laying of such shinglesmust be done carefully, since, otherwise, the interlocking portions.

may be broken off, or torn awayfrom the main body. Even when suchshingles are carefully handled, however, it may-be difficult to makethem lie fiat or snugly against the roof particularly at theinterlocking portions. When laying so-called roll roofing, the usualbituminized rag felts may give trouble over sharp comers because thefelt base tends to crack or open up under sharp flexing or to. become sogreatly weakened as to tear off under slight provocation.

It has been established that a bituminized felt whose felt base is madelargely or entirely from refinedcellulose pulp in a substantially unhy-6C1 drated condition represents a vast improvement over the conventionalbituminized rag felt. For instance, the bituminization of a waterlaidfelt whereinto substantially unhydrated refined wood pulp having analpha cellulose content of say, at least about 93%, has entered as aprincipal raw material gives rise to a product of excellent moldability,pliability, and such high tear resistance as to be consideredpractically tearproof. Moreover, the felt itself can be folded 'onitself without cracking. We have now found that even when therefined butsubstantially unhydrated cellulosepulp is used as a subordinate fibrouscomponent in the felt-making furnish, that is, in amount even less thanby weight of the dry fibrous materials constituting the furnish, it ispossible to arrive at felts "which, too, are practically as resistant tocracking when folded onto, themselves as felts consisting mostly ofrefined cellulose pulp in substantially unhydrated condition, and which,when bituminized, display remarkably better properties than the usualbituminized rag felts. Indeed, we have found that the use of as littleas 20% to 30% by weight of refined but substantially unhydratedcellulose pulp in a felt-making furnish is all that is necessary toenhance the pliability and folding endurance of the bituminized feltenormously even though the tear resistance of the bituminized felt isnot so markedly benefited. For many roofing purposes, however, theultimate or best tear resistance in the bituminized felt may not bevital, but an enhanced pliability or moldability may be of tremendousadvantage. The point is that by using a preponderant proportion of ragsand a subordinate proportion of refined but substane tially unhydratedcellulose pulp as raw materials in the felt-making furnish, it ispossible to arrive at bituminized felts which are surprisingly superiorto the usual bituminized rag felts for danger of being cracked or trimat their interlocking portions, whereat they are weakest, and can bemade to lie flatly against the roof more easily than the usual rag feltbase shingles. It is thus seen that we accomplish the desired ends witha minimum usage of refined cellulose pulp, which is a far more expensiveraw material than wool fiber, is added to the felt-making furnish,

the sharp-bend flexibility is improved, but the strength of the felttends to drop rapidly. On the other hand, the simple addition of compar-"atively little refined cellulose pulp to the feltmaking furnish affordsan inexpensive way of both realizing sharp-bend flexibility in the feltand of improving the toughnessof the bituminized felt. The interestingaspect of the results which we secure is that the effect of the refinedbut substantially unhydrated cellulose pulp is not largely or entirelyobliterated by the larger proportion of hydrated but unrefined rag pulpentering into the felt-making furnish, which, if it were made from onlyrags as raw material, would yield felt tending to flake or crack openvery badly on the surface when folded on itself. In

other words, it might reasonably be expected,

that the great dilution with inferior hydrated pulp which the refinedbut substantially unhydrated pulp undergoes would give rise tobituminized felts possessing little, if any, advantage over the usualbituminized rag felts. Apparently, the softness and other desirablequalities inhering in the refined but substantially unhydrated pulppersist in a felt containing only about 10% to 20% of such pulp and "areresponsible for the qualities of good moldability, pliancy, and tearresistance in a bituminized felt. In other words, such impurities andhydrated cellulose as arise from the rag pulp in the felt-making furnishevidently remain external to the refined fibers, that is, do not existin intimate association with the fiber wall of the refined fibers asimpurities occur in an unrefined wood pulp, for

instance.

While theremay be various procedures falling within the purview ofthepresent invention, we shall give typical practice such as may beadvantageously adopted inpreparinga bituminized roofing felt inaccordance with our invention. A beater engine may be charged with cheaprags such as are customarily employed for felt-making purposes and withsuflicient water to ensure circulation of the mass. The beater roll maybe put in operation with its knives or bars so clearing the bed-plate asto cut or reduce the rags sufliciently to yield a smooth .pulp orhalfstuff satisfactory for felt formation. At this time, the

' the furnish even though the rags have inevitably refined pulp of woodor other origin having an alpha cellulose content of say, at least about93%.

It is thus seen that the refined pulp is maintained in substantiallyunbeaten or unhydrated statein undergone considerable hydration orgelatinization wliilebeing reduced to a pulp. The mixed furnish may thenbe run off on a felt-making machine, the resulting felt bituminized asby passage through a bath of molten asphalt having a melting point ofabout 130 F. (ball and ring test) and at a temperature of about 385 to400 F. in the bath, and the bituminized felt may be coated with blownasphalt or the like and be surfaced with ornamental, weather-resistingmaterial, such as crushed, colored slate or its equivalent.

The refined cellulose pulp employed in the feltmaking furnish of thepresent invention may be prepared as by exposing the usual chemical woodpulps, e. g., kraft or sulphite pulp, to the action of alkaline liquorsunder conditions resulting in 'an extraction of a substantial proportionof the non-alpha cellulose components from the pulp, for instance,bringing the alpha cellulose content of the pulp to at least, say, about93% or greater. In some instances, as when sulphite pulp is beingrefined, a dilute alkaline liquor and comparatively high temperature maybe advantageously relied upon in bringing about this refinement. 0n theother hand, a pulp may be refined in strong alkaline liquors atcomparatively low temperatures, for instance, in liquors of sumci'entconcentration to mercerize the pulp. In any case, however, the refinedpulp entering into the felt-making furnish should be maintained in asubstantially'unhydrated condition'in order to yield a bituminized sheetof the desired characteristics. When pulps are refined in alkalineliquors, the impurities existing in intimate asso- 5 ciation with thefiber wall are evidently leached out, leaving the fiber wall in a moreor less etched condition. The softness and flexibility of the refinedfibers evidently remain unimpaired even when such fibers are commingledwith comp'ara- 2 tively impure hydrated rag pulp, whose impurities andhydrocellulose appear to remain as'a phase external to the refined pulpfibers.

We claim: I 1. A bituminized, waterlaid felt whose fibrous 5 base ismade up essentially of at least about 60% to 85% of hydrated rag pulpand about 40% to 15% of substantially unhydrated wood pulp having analpha cellulose content of at least about 2. A process which comprisesbeating unrefined rags in water to form a hydrated, feltablepulp,admixing with said pulp substantially unhydrated wood pulp 'having analpha cellulose content of at least about 93% in amount to produce afurnish containing only about 15% to 40% of said wood pulp, making awaterlaid felt from said furnish, and bituminizing the felt.

. MILTON O. SCHUR.

WALTER L. HEARN.

